/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.server.ai.mission;

import java.util.logging.Logger;

import javax.xml.stream.XMLStreamException;

import net.sf.freecol.common.io.FreeColXMLReader;
import net.sf.freecol.common.io.FreeColXMLWriter;
import net.sf.freecol.common.model.Colony;
import net.sf.freecol.common.model.GameOptions;
import net.sf.freecol.common.model.Goods;
import net.sf.freecol.common.model.GoodsContainer;
import net.sf.freecol.common.model.GoodsType;
import net.sf.freecol.common.model.IndianSettlement;
import net.sf.freecol.common.model.Location;
import net.sf.freecol.common.model.Direction;
import net.sf.freecol.common.model.Market;
import net.sf.freecol.common.model.Player;
import net.sf.freecol.common.model.Specification;
import net.sf.freecol.common.model.Tension;
import net.sf.freecol.common.model.Unit;
import net.sf.freecol.common.model.pathfinding.CostDeciders;
import net.sf.freecol.common.util.LogBuilder;
import net.sf.freecol.server.ai.AIMain;
import net.sf.freecol.server.ai.AIMessage;
import net.sf.freecol.server.ai.AIUnit;


/**
 * Mission for demanding goods from a specified player.
 */
public class IndianDemandMission extends Mission
{

    private static final Logger logger = Logger.getLogger( IndianDemandMission.class.getName( ) );

    /** The minimum amount of goods to demand. */
    private static final int GOODS_DEMAND_MIN = 30;

    /** The tag for this mission. */
    private static final String tag = "AI native demander";

    /** The colony to demand from. */
    private Colony colony;

    /** Whether the demand has been made or not. */
    private boolean demanded;


    /**
     * Creates a mission for the given <code>AIUnit</code>.
     *
     * @param aiMain The main AI-object.
     * @param aiUnit The <code>AIUnit</code> this mission is created for.
     * @param target The <code>Colony</code> receiving the gift.
     */
    public IndianDemandMission( AIMain aiMain, AIUnit aiUnit, Colony target )
    {
        super( aiMain, aiUnit, target );

        this.demanded = false;
    }

    /**
     * Creates a new <code>IndianDemandMission</code> and reads the given
     * element.
     *
     * @param aiMain The main AI-object.
     * @param aiUnit The <code>AIUnit</code> this mission is created for.
     * @param xr The input stream containing the XML.
     * @throws XMLStreamException if a problem was encountered during parsing.
     * @see net.sf.freecol.server.ai.AIObject#readFromXML
     */
    public IndianDemandMission( AIMain aiMain, AIUnit aiUnit,
                                FreeColXMLReader xr ) throws XMLStreamException
    {
        super( aiMain, aiUnit );

        readFromXML( xr );
    }


    /**
     * Checks if the unit is carrying a tribute (goods).
     *
     * @return True if the unit is carrying goods.
     */
    private boolean hasTribute( )
    {
        return hasTribute( getAIUnit( ) );
    }

    /**
     * Checks if a unit is carrying a tribute.
     *
     * @param aiUnit The <code>AIUnit</code> to check.
     * @return True if the unit is carrying goods.
     */
    private static boolean hasTribute( AIUnit aiUnit )
    {
        return aiUnit.getUnit( ).hasGoodsCargo( );
    }

    /**
     * Selects the most desirable goods from the colony.
     *
     * @param target The colony.
     * @return The goods to demand.
     */
    public Goods selectGoods( Colony target )
    {
        final Specification spec = getSpecification( );
        Tension.Level tension = getUnit( ).getOwner( )
                .getTension( target.getOwner( ) ).getLevel( );
        int dx = spec.getInteger( GameOptions.NATIVE_DEMANDS ) + 1;
        final GoodsType food = spec.getPrimaryFoodType( );
        Goods goods = null;
        int amount = capAmount( target.getGoodsCount( food ), dx );
        if ( tension.compareTo( Tension.Level.CONTENT ) <= 0
                && target.getGoodsCount( food ) >= amount )
        {
            return new Goods( getGame( ), target, food, amount );
        }
        else if ( tension.compareTo( Tension.Level.DISPLEASED ) <= 0 )
        {
            Market market = target.getOwner( ).getMarket( );
            int value = 0;
            for ( Goods currentGoods : target.getCompactGoods( ) )
            {
                int goodsValue = market.getSalePrice( currentGoods );
                if ( currentGoods.getType( ).isFoodType( )
                        || currentGoods.getType( ).isMilitaryGoods( ) )
                {
                    continue;
                }
                else if ( goodsValue > value )
                {
                    value = goodsValue;
                    goods = currentGoods;
                }
            }
            if ( goods != null )
            {
                goods.setAmount( capAmount( goods.getAmount( ), dx ) );
                return goods;
            }
        }
        else
        {
            // Military goods
            for ( GoodsType preferred : spec.getGoodsTypeList( ) )
            {
                if ( preferred.isMilitaryGoods( ) )
                {
                    amount = target.getGoodsCount( preferred );
                    if ( amount > 0 )
                    {
                        return new Goods( getGame( ), target, preferred,
                                          capAmount( amount, dx ) );
                    }
                }
            }
            // Storable building materials (what do the natives need tools for?)
            for ( GoodsType preferred : spec.getStorableGoodsTypeList( ) )
            {
                if ( preferred.isBuildingMaterial( ) )
                {
                    amount = target.getGoodsCount( preferred );
                    if ( amount > 0 )
                    {
                        return new Goods( getGame( ), target, preferred,
                                          capAmount( amount, dx ) );
                    }
                }
            }
            // Trade goods
            for ( GoodsType preferred : spec.getStorableGoodsTypeList( ) )
            {
                if ( preferred.isTradeGoods( ) )
                {
                    amount = target.getGoodsCount( preferred );
                    if ( amount > 0 )
                    {
                        return new Goods( getGame( ), target, preferred,
                                          capAmount( amount, dx ) );
                    }
                }
            }
            // Refined goods
            for ( GoodsType preferred : spec.getStorableGoodsTypeList( ) )
            {
                if ( preferred.isRefined( ) )
                {
                    amount = target.getGoodsCount( preferred );
                    if ( amount > 0 )
                    {
                        return new Goods( getGame( ), target, preferred,
                                          capAmount( amount, dx ) );
                    }
                }
            }
        }

        // Have not found what we want
        Market market = target.getOwner( ).getMarket( );
        int value = 0;
        for ( Goods currentGoods : target.getCompactGoods( ) )
        {
            int goodsValue = market.getSalePrice( currentGoods );
            if ( goodsValue > value )
            {
                value = goodsValue;
                goods = currentGoods;
            }
        }
        if ( goods != null )
        {
            goods.setAmount( capAmount( goods.getAmount( ), dx ) );
        }
        return goods;
    }

    private int capAmount( int amount, int difficulty )
    {
        return Math.min( Math.max( amount * difficulty / 6, GOODS_DEMAND_MIN ),
                         GoodsContainer.CARGO_SIZE ); // One load of goods max
    }

    private static IndianSettlement getHome( AIUnit aiUnit )
    {
        return aiUnit.getUnit( ).getHomeIndianSettlement( );
    }

    /**
     * Why would this mission be invalid with the given unit?
     *
     * @param aiUnit The <code>AIUnit</code> to test.
     * @return A reason why the mission would be invalid with the unit,
     *     or null if none found.
     */
    private static String invalidMissionReason( AIUnit aiUnit )
    {
        String reason = invalidAIUnitReason( aiUnit );
        IndianSettlement home;
        return ( reason != null )
                ? reason
                : ( ( home = getHome( aiUnit ) ) == null || home.isDisposed( ) )
                ? "home-destroyed"
                : null;
    }

    /**
     * Why would an IndianDemandMission be invalid with the given
     * unit and colony.
     *
     * @param aiUnit The <code>AIUnit</code> to test.
     * @param colony The <code>Colony</code> to test.
     * @return A reason why the mission would be invalid with the unit
     *     and colony or null if none found.
     */
    private static String invalidColonyReason( AIUnit aiUnit, Colony colony )
    {
        String reason = invalidTargetReason( colony );
        if ( reason != null ) return reason;
        final Unit unit = aiUnit.getUnit( );
        final Player owner = unit.getOwner( );
        Player targetPlayer = colony.getOwner( );
        switch ( owner.getStance( targetPlayer ) )
        {
            case UNCONTACTED:
            case PEACE:
            case ALLIANCE:
                return "bad-stance";
            case WAR:
            case CEASE_FIRE:
                Tension tension = unit.getHomeIndianSettlement( )
                        .getAlarm( targetPlayer );
                if ( tension != null && tension.getLevel( )
                        .compareTo( Tension.Level.CONTENT ) <= 0 ) { return "happy"; }
                break;
        }
        return null;
    }

    /**
     * Why would this mission be invalid with the given AI unit?
     *
     * @param aiUnit The <code>AIUnit</code> to check.
     * @return A reason for invalidity, or null if none found.
     */
    public static String invalidReason( AIUnit aiUnit )
    {
        return invalidMissionReason( aiUnit );
    }

    /**
     * Why would this mission be invalid with the given AI unit and location?
     *
     * @param aiUnit The <code>AIUnit</code> to check.
     * @param loc The <code>Location</code> to check.
     * @return A reason for invalidity, or null if none found.
     */
    public static String invalidReason( AIUnit aiUnit, Location loc )
    {
        String reason = invalidMissionReason( aiUnit );
        return ( reason != null )
                ? reason
                : ( loc instanceof Colony )
                ? invalidColonyReason( aiUnit, ( Colony ) loc )
                : ( loc instanceof IndianSettlement )
                ? invalidTargetReason( loc, aiUnit.getUnit( ).getOwner( ) )
                : Mission.TARGETINVALID;
    }


    // Implement Mission
    //   Inherit dispose, getBaseTransportPriority, isOneTime

    /**
     * {@inheritDoc}
     */
    @Override
    public Location getTransportDestination( )
    {
        return null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Location getTarget( )
    {
        return ( this.demanded ) ? getUnit( ).getHomeIndianSettlement( )
                : this.colony;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setTarget( Location target )
    {
        if ( target instanceof Colony )
        {
            this.colony = ( Colony ) target;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Location findTarget( )
    {
        return getTarget( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String invalidReason( )
    {
        return invalidReason( getAIUnit( ), getTarget( ) );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Mission doMission( LogBuilder lb )
    {
        lb.add( tag );
        String reason = invalidReason( );
        if ( reason != null ) return lbFail( lb, false, reason );

        final AIUnit aiUnit = getAIUnit( );
        final Unit unit = getUnit( );
        final IndianSettlement is = unit.getHomeIndianSettlement( );
        Direction d;

        while ( ! this.demanded )
        {
            Unit.MoveType mt = travelToTarget( getTarget( ), null, lb );
            switch ( mt )
            {
                case MOVE_HIGH_SEAS:
                case MOVE_NO_MOVES:
                case MOVE_NO_REPAIR:
                case MOVE_ILLEGAL:
                    return lbWait( lb );

                case MOVE_NO_TILE:
                    return this;

                case ATTACK_SETTLEMENT: // Arrived?
                    d = unit.getTile( ).getDirection( getTarget( ).getTile( ) );
                    if ( d != null ) break; // Yes, arrived at target
                    // Fall through
                case ATTACK_UNIT: // Something is blocking our path
                    Location blocker = resolveBlockage( aiUnit, getTarget( ) );
                    if ( blocker == null )
                    {
                        moveRandomly( tag, null );
                        continue;
                    }
                    d = unit.getTile( ).getDirection( blocker.getTile( ) );
                    if ( AIMessage.askAttack( aiUnit, d ) )
                    {
                        return lbAttack( lb, blocker );
                    }
                    continue;

                default:
                    return lbMove( lb, mt );
            }

            // Load the goods.
            lbAt( lb );
            Colony colony = ( Colony ) getTarget( );
            Player enemy = colony.getOwner( );
            Goods goods = selectGoods( colony );
            GoodsType type = ( goods == null ) ? null : goods.getType( );
            int amount = ( goods == null ) ? 0 : goods.getAmount( );
            if ( goods == null )
            {
                if ( ! enemy.checkGold( 1 ) )
                {
                    return lbDone( lb, false, "empty handed" );
                }
                amount = enemy.getGold( ) / 20;
                if ( amount == 0 ) amount = enemy.getGold( );
            }
            this.demanded
                    = AIMessage.askIndianDemand( aiUnit, colony, type, amount );
            if ( this.demanded && ( goods == null || hasTribute( ) ) )
            {
                if ( goods == null )
                {
                    return lbDone( lb, false, "accepted tribute ",
                                   amount, " gold" );
                }
                lb.add( ", accepted tribute ", goods );
                return lbRetarget( lb );
            }

            // Consider attacking if not content.
            int unitTension = ( is == null ) ? 0 : is.getAlarm( enemy ).getValue( );
            int tension = Math.max( unitTension,
                                    unit.getOwner( ).getTension( enemy ).getValue( ) );
            d = unit.getTile( ).getDirection( colony.getTile( ) );
            if ( tension >= Tension.Level.CONTENT.getLimit( ) && d != null )
            {
                if ( AIMessage.askAttack( aiUnit, d ) ) lbAttack( lb, colony );
            }
            return lbDone( lb, false, "refused at ", colony );
        }

        // Take the goods home
        for ( ; ; )
        {
            Unit.MoveType mt = travelToTarget( getTarget( ),
                                               CostDeciders.avoidSettlementsAndBlockingUnits( ), lb );
            switch ( mt )
            {
                case MOVE_HIGH_SEAS:
                case MOVE_NO_MOVES:
                case MOVE_NO_REPAIR:
                case MOVE_ILLEGAL:
                    return lbWait( lb );

                case MOVE_NO_TILE:
                    return this;

                case MOVE: // Arrived
                    break;

                default:
                    return lbMove( lb, mt );
            }

            // Unload the goods
            lbAt( lb );
            GoodsContainer container = unit.getGoodsContainer( );
            for ( Goods goods : container.getCompactGoods( ) )
            {
                Goods tribute = container.removeGoods( goods.getType( ) );
                is.addGoods( tribute );
            }
            return lbDone( lb, false, "unloaded tribute" );
        }
    }


    // Serialization

    private static final String COLONY_TAG = "colony";
    private static final String DEMANDED_TAG = "demanded";


    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeAttributes( FreeColXMLWriter xw ) throws XMLStreamException
    {
        super.writeAttributes( xw );

        if ( this.colony != null )
        {
            xw.writeAttribute( COLONY_TAG, this.colony.getId( ) );
        }

        xw.writeAttribute( DEMANDED_TAG, this.demanded );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void readAttributes( FreeColXMLReader xr ) throws XMLStreamException
    {
        super.readAttributes( xr );

        this.colony = xr.getAttribute( getGame( ), COLONY_TAG,
                                       Colony.class, ( Colony ) null );

        this.demanded = xr.getAttribute( DEMANDED_TAG, false );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getXMLTagName( ) { return getXMLElementTagName( ); }

    /**
     * Gets the tag name of the root element representing this object.
     *
     * @return "indianDemandMission".
     */
    public static String getXMLElementTagName( )
    {
        return "indianDemandMission";
    }
}
